The present invention relates to a folding drum for folding material, in particular for a printing press. The folding drum is mounted rotatably on its longitudinal axle and has a folding-blade spindle.
It is known for a printing press to comprise a folder, with which folds can be formed on printed material, in particular paper. A folder of this type comprises a folding drum, with which, in particular, longitudinal folds can be made in materials which have already been cut and prefolded. For this purpose, the folding drum has a folding-blade spindle, to which a folding blade is attached. The folding drum is mounted rotatably on its longitudinal axle and the folding-blade spindle is coupled to the longitudinal axle of the folding drum, with the result that the rotational movement of the folding drum is transmitted to the folding-blade spindle. As the longitudinal axle of the folding-blade spindle extends parallel to the longitudinal axle of the folding drum, the mass of the folding-blade spindle generates a radially outwardly acting centrifugal force during rotation of the folding drum. This centrifugal force represents a loading for the folding-blade spindle, in particular for its bearing, which loading can lead to disadvantages, in particular to high wear.
The invention is therefore based on the object of specifying a folding drum, in which these disadvantages are at least reduced.
The folding drum according to the invention serves to fold material, in particular in a printing press, and is mounted rotatably on its longitudinal axle. It has a folding-blade spindle, the longitudinal axle of which is coupled to the longitudinal axle of the folding drum and is spaced apart from the longitudinal axle of the folding drum. Furthermore, the folding drum comprises a force generation means for generating a relief force. The relief force is opposed to a centrifugal force which occurs in a rotating folding drum as a result of the co-rotating folding-blade spindle. The influence of the centrifugal force on the folding-blade spindle, and, in particular, on a bearing of the folding-blade spindle, is reduced by the generation of the relief force. As a result of the reduction in the radially outwardly directed loading of the folding-blade spindle, the service life of its bearing can be increased advantageously. It is also possible to increase the rotational speed of the folding drum, and therefore the processing speed, if required, without obtaining a disadvantageous loading of the folding-blade spindle as a result. On account of the configuration according to the invention of the folding drum, further supporting bearings for supporting the folding-blade spindle can advantageously be omitted. This is true, in particular, in the case of the use of groove ball bearings for mounting the folding-blade spindle.
The force generation means is advantageously coupled to the longitudinal axle of the folding drum. This ensures that the force generation means can rotate together with the folding drum, and likewise together with the folding-blade spindle. Here, the force generation means can be configured in such a way that it adapts the relief force to the rotational speed, and therefore to the centrifugal force which acts on the folding-blade spindle.
In one particularly advantageous refinement of the invention, the force generation means is guided by means of a guide which is configured in such a way that it permits the movement of the force generation means in the direction of the relief force and largely prevents a movement in at least one other direction. The guide therefore ensures that the relief force which can be generated by the force generation means can act completely counter to the centrifugal force which is generated by the folding-blade spindle.
There are particularly advantageous journals which are arranged on the outside on the opposite folding-drum sides for the rotatable mounting of the folding drum in a holding device. Moreover, the folding drum can have at least one extension of the journals into the interior of the folding drum. The guide is realized as a passage in this at least one extension. The guide can be realized in a particularly simple and reliable manner by way of this arrangement. Furthermore, both the rotation of the force generation means together with the rotation of the folding drum and the guidance of the force generation means can take place for the sake of simplicity via the at least one journal extension. As a result of this refinement of the at least one journal extension, the latter can therefore advantageously assume two functions at the same time.
In one advantageous development of the invention, the guide is provided with lubricating varnish and/or with a coating. The lubricating varnish makes largely frictionless sliding possible of the guided force generation means in the guide. The coating is advantageously selected in such a way that it prevents corrosion of the guide and/or of the force generation means.
In a further particularly advantageous refinement of the invention, the folding-blade spindle is divided into at least two part folding-blade spindles which are arranged next to one another. Here, the force generation means is configured in such a way that it acts between the part folding-blade spindles. In this way, the loading of the folding-blade spindle, in particular with respect to its bearing, and the effect of the centrifugal force which is generated by it during rotation can be reduced further.
The force generation means advantageously has at least one spring. A relief force which is independent of the rotational speed of the folding drum can be generated with at least one spring of this type. The at least one spring can be realized inexpensively and has a low weight. In addition or as an alternative, the force generation means can have at least one compensating mass. As a result, the generation of the relief force can be realized in a particularly simple and effective manner. The relief force which counteracts the centrifugal force can be set with the compensating mass as a function of the rotational speed of the folding drum. As the rotational speed increases, the level of the relief force is adapted automatically to the increasing level of the centrifugal force.
Further advantageous refinements and developments of the invention can be gathered from the description, with reference to the drawings.
Identical or functionally identical elements are provided with the same reference numerals in the figures, unless otherwise specified.